Posthole digger



Dec. 14, 1948. w. J. McGARR 2,456,208

POSTHOLE DIGGER Filed Feb. 14, 1945 2 Sheets-Sheet 2 3mm W.J.McGARR M 44 M MUNN,L|DDY 8 GLACCUMW Patented Dec. 14, 1948 UNITED STATES. PATENT GFFICE POSTHOLE BIGGER Walter James McGarr, Cordele, Ga.

Application February 14, 1945, Serial No. 577,915 3 Claims. (01. 255-22) This invention relates to a post hole digger.

An object of the invention is the provision of a device which may be readily attached to a tractor so that the borer may be driven from the power take-off of said tractor, while the borer is advanced into the ground by means of hydraulic power, said borer being retracted to an inoperative position, eitherbya spring in cooperation with the fluid which has advanced the bit or borer, or the bit may be retracted by the hydraulic fluid per se.

Another object of the invention is the provision of a post hole digger, which is adapted to be attached to a tractor with the bit being revolved from the power take-off, while the bit is advanced into the ground by means of hydraulic power operating in a cylinder against the piston connected with the bit, a second cylinder being employed and provided with a piston which moves in opposite directions from the first mentioned piston, so that when the bit has been advanced to its limit in the ground said-bit'may be returned to its retracted'position when the hydraulic power has been applied to the second mentioned piston, saidpiston being operatively connected together by means of a cable trained on pulleys which rotate in opposite directions.

A further object of the invention is the provision of a power driven post hole digger in which a bit is advanced into the ground during rotation by means of a piston operating in'a cylinder through hydraulic pressure, said bit being connected to the piston by means of a shaft which is capable of rotating while the piston is non-rotatable in the cylinder, means being employed for retracting the piston shaft and bit after the hole has been dug.

A still further object of the invention is the provision of a post hole digger adapted to be attached to a tractor, said bit being revolved by operative connections between a shaft carrying the bit and the power take-off of the tractor, said bit being reciprocated by a piston having swivel connections with a shaft, and a second cylinder containing a piston, and a cable connecting the pistons and trained over pulleys rotatable in opposite directions, so that when one This invention will be best understood from a consideration of-the following detailed descrip tion, in View of the accompanying drawings;

forming a part of the specification; nevertheless,

it is to be understood that the invention is not confined to the disclosure, being susceptible of such changes and modifications as define no ;material departure from the salient features of showing my post hole digger applied in operative relation thereto.

Figure 2 is a conventional vertical sectional View of the device. It is taken at right angles to Fig. 3 but for the purpose of illustration the two cylinders, shown in staggered relationship.

on Fig. 5, are located in a common plane together with the rotary drive shaft in order to facilitate the description of the operation of said parts.

Fig. 3,is a fragmentary vertical section at right angles to the section in Fig. 2.

Fig. 4 is a fragmentary end view in elevation of the'upper portion of the device.

Fig. 5 is a section taken along the line 5-5 of Fig.3.

Fig. 6 isa view in perspective of the upperv portion of the device with the cap or closure removed.

Fig. 7 is a bottom plan. view of the cap.

Fig. 8 is a plan view after the cap or closure and the valve have been removed.

Referring more particularly to the drawings,

l0; designates generally a tractor which is .ca-?

pable of being moved under its own power from one position to another for digging postholes along a predetermined line.

This tractor is provided with a shaft ll form-'- ing the power take-01f from the tractor. To this shaft is attached a pulley l2 which drives a belt from the cover plate and extend upwardly to a housing ,23 which is above the cylinders and is supported by said cylinders. These cylinders may be made independently of the cover plate 20 and a bottom wall 24 of the housing 23. These cylinders may be threaded into openings in the cover plateand also in the wall 24. The shaft I5 is;

mounted in bearings in the housing l8, and at its inner end is provided with a tapered gear 26 meshing with a ring gear 27 which is secured at 28 to a collar 29 formed integrally with a sleeve 30 which is located below the cylinder 2| and in axial alinement therewith so that when the gear 21 is revolved the sleeve 30 will likewise be revolved. A keyway 3| is formed in a shaft 32 mounted for reciprocation within the cylinder 2|. A key 33' carried by? t1'l835168VE: 3D; rides i'nathel keyway 3'1wh'en"th'e sli'aft'32 is moved downwardly or upwardly. Thus, the shaft 32 will be re,- volved when the sleeve 30 is revolved by the ring" gear 21. A bushing 35 is mounted in an opening: in a plate 36 which is bolted at 31 to the upper portion of the housing l8. A bushing" 38 em? braces the sleeve 35s at its lower. end and. is; dis posed within a cylindrical depending portion 39 of the housing IS. A packing gland do is threaded into the lower end of the member 39 for sealing the lowen end; of: the; housing: against a loss: of; oil.. Since:hea-vy oilissnormallyemployeddn the: cylinder 2+ some: of this Ofl:Wi11.WOIk its waylintoi the housing: t8 for'lubricat-ing; the movable ele-W ments: in: said: housing;

At bitwgenerally designatedby. the: numeral W is removably connected to the outer projecting: end of the shaft 32 by a shear. pin 42;, andi this sheen-pin a'lso oonnectsia wiperr lfi to the upper end: of 17h6;bib.- The bit may be: of any wella known type, and is provided; with spiral: flanges 431:: which will remove? dirtfrom: the hole: when itisrloosened by.-the;tip- 44 on thel-lowenendlof the? bitil. This tip" is pinned: as shown; at: 451: to: the: lower errdi of the: bit so that: it mayg'be' removed. orreplaceiif; necessaryz.

A piston: is. supportedz byone endi 5l' at: as cable: generally: designated by; the numeral; 52;. The cable is provided with a yoke 53 which; is pivotally connected at: 54 to; aa finger-f5 Sspnoi eating upwardly from the pistom 50..

'Iiheesliaftfi2-:isprovidediwithl auredu'ced portion to which the pistonjflzis SWiYBHQ/COIIHBGCBdLSE' thattwhile the shaft't21isarotatedaandzlowererhthe piston 58 will remain stationary except. fon'itsu reciprocation; in'. the. cylinder Z I. Bearings: 6| andi6-2rane located: on; the reduced: portiorn an: of: the shaft 32 provided with spacers 63 and: EA: im the form ofi collarst. The. collar: 64 is supported 011.8% cup-shapedr member resting: om as collar 66 at the upper end-.01; the-Eshaft' 32;

The: cable. 5| is trained; or: a; pulley. 6']; keyed to: a shaft: 68* mounted; imtheahousingt 23; (Eigs; 2'; and 399.. AiSQUOITd pulley 69. alsmlocatediim theihousing z3 a-ndiiswa=lso secured to the-shaft 68s A cable 5Ia is trained on the: pulley 69,. butt-he oppositedirection to the: training ofi the ca'BlelSl om thespulley fiihsoithatiwhen. theseepul; leys revolve: int the: same: direction. the! cable on; one-pulley: will be wound thereon, while the cableon: the other pulleywillibevunwound; The shaft:- G'BIis supported by plugs-on" bearingsfl fli in the side walls: of: the housing: Z3i. A partition) Till divides the: housing into two. separate. chambers 12 .andi 13 so that the chamber 1 2 isisol'ated from the chamber t3 forr a1. purpose: which: will! be presently explained;

Al piston: generally designated by. the numerall t5 has. an: eye. 16 pivotally connected to a:- yoke. 131. which: secured: t'oithel lower: end? of? thee cable? 5111:. A; cup shaped. member '18 is supported. a; pin: T9: the: member- 15"; and. is; adaptedi to; close. the: lbwer: end. of; the. cylinder 22 Thus it will beseen; that when; power 37gb the key 33 will rotate the shaft 32, and if pressure is exerted on the piston 50 the shaft 32 will be forced downwardly as will be the member 4| so that a hole will be dug in the ground. The pressure employed for driving the shaft 32 downwardly is a liquid under pressure, and when the shaft is moved downwardly the piston 15 will be moved upwardly. On the other hand, when the fluid pressure is exerted against the piston 15, saidpi'stons will." hermovedldowrrwardl'y while the shaft 32*an'dthe piston 5'0-will'*be-raised, provision being made for the discharge at that time of the liquid in the upper end of the cylinder 2i.

Thethottom of the housing 23 is provided with an opening through which liquid passes to and from-the cylinder 22. A passage 8| is formed in thebottom. oilthelhousing 23 and above the cylinder 2| so that liquid from the chamber I2 will pass to and from the upper end of the cylinder 2|.

The-.uppen endtof the housing is. provided with aavalve. casing whichhasa.removable.cover 82. The cover, andlikewise:thetop ii3l ofithe housing, is provided with complementarily formed. semncircular grooves: 84) and 85 respectively, so. that. when, theatop is.-in, place a. circular passage will be; formed. to receive. a. valve. 86.. This. valve. is. provided with-a pair. of annualgrooves. 81 and 88... The top of the: housing 83- is provided with. a. semi-circular-groove-fit matching a semiecircular groove 9| and the cover plate 82mto iornra cylinr dricai.. passage: 86a.- for. incoming, liquid. under pressure; 'Qnee end. of. this passage: is: closed, as shownat 89: (Fig: 4) while: the: other. endris con:-- necteditozanzinletpipe 9.2. (Fig; 1;)- for. supplying, liquid under pressure tosaid. passage from apump: (not shown); operated by the. engine of. the: tractor.-. A. second. passage. generally designated. by -the numeral 93 is closed at one end 88 a (Fig,-.. 4-): and? is formed. by: a-. semi-cylindrical groove. 9.4- in; theitop' 83i of the housing: 2.3; andzby a semicylindricalignonve 95 :in;the coverplate. 82- topme vid'e at cylindrical passagethrough which: the liquid: is discharged; intoa. pipe 96- which. carries.

- spentzliquid baCRitOLthBIIOW pressure sideof; the.

Aniinspectiorr-ofiliigafi will show'that the. top 83: is.providedtwithiaachannel 9;"! which leads from the crosswisechannel 8.6m to the centerchannel. M: sothat when. the groove; 87 of the valve 86.: aiines withapassagerfi?! liquid under pressurewill. flow tothecylinder 2A! and cause: the piston- 5111;, anddikewisez the shaftSZ; to be lowered: When: theigroove 81'! alinesv with the-exhaust passage 99 in: the top* 83. liquidwill be: discharged: from the cylinder 2.1 to! the passage: formed. bythe: semi? circular grooves: 914: and H5. whereby the; fluid is: dischargedthrough therpipe Sbfibaclc to; the. pump.

The groove 88 in: the valve 86 is adapted to Arline: with; crosswise. inlet passage H10 in thetop 88', andlsince-this passage connects theinlet passage;- 8521 with a; passage ['01 (Fig. 3) communicating'jwith chamberr'tii over the; cylinder 22:. Fluid: under: pressure will drive. the; piston 15 downwandly... On. the other hand; when. the;

groove? 88' inth'e valve; 86 alines; with an exhaust pipe 1:02.111 thetop 83:the:fluid:in the cylinder 22' Will be: dischargediintovthe-z passage. 93: formed. by the: semi-circular grooves; 941 and 95, and will. enterthe. exhaust pipe: 9.6- to be returned to the.

p mp.

It will be noted from Figs.fiithatthevpassages 93K and! lloflirr. the top- 83? are. sufli'cientl'y extensive to permit: the grooves 81 and 88 respectivelytorthie. shaft l.5= the gearsi 26 and l'l through. 753 to: allhw fluid tm enter: either chamber. 12 or T3 and similarly passages 99 and I02 permit the fluid to be discharged from said chambers.

The valve 86 is operated manually by a lever I03 pivoted at Hill on the housing 23. This lever is operated by a rod H05 which extends rearwardly and is provided with an operating handle I 06 adjacent the seat of the driver. In other words, the valve 86 is shifted longitudinally within its cylindrical passage designated by the numerals 84 and 85 in Fig. 2 for properly positioning said valve for the discharge of fluid from one cylinder while causing fluid under pressure to enter the other cylinder.

The operation of the device shown in Figs. 1 to 8 inclusive is as follows:

Power is supplied to the shaft I5 in any approved manner, as by a clutch mechanism from the power take-ofi of the tractor which operates the belt l3 trained on the pulleys I 2 and i l. The shaft 32 is then rotated together with the borer 4|.

The valve 86 is shifted by the rod I05 so that the groove 8'! therein will aline with the passage 91 so that liquid under pressure from a supply pump will enter the passage 98 in the chamber 12, hence the liquid will enter the passage 8| in the bottom 24 of the housing 23. This liquid under pressure, preferably oil, will act on the piston 50, causing the shaft 32 to descend as well as the borer 4i, hence a hole will be out into the ground. When the shaft and boring tool have reached their lower limit and the wiper '33 has removed the dirt away from the top of the hole the shaft 32 may be returned to its normal inoperative position by moving the valve 86 to a position whence the groove 88 will aline with the passage I90 (Fig. 6), so that fluid under pressure will be directed into the cylinder 22 and against the piston so that the piston will be moved downwardly to the position shown in Fig. 2 while the piston 50 will be elevated.

The power take-ofi is disconnected from the pulley [2 by a clutch mechanism (not shown), and the tractor may then be moved to the next position for drilling a hole and the operations will be repeated.

The piston may be manually operated through a system of gearing and a large hand wheel.

The cylinders 2| and 22 are diagonally disposed as shown in Fig. 5 in order that the cables 5| and EM may be projected into said cylinders since the cables descend from opposite sides of the pulleys 6i and 69.

It will be appreciated that since the shear pin 45 may be readily removed new tips may be applied to the lower end of the bit 4! or a different type of tip may be substituted when desired.

Furthermore, this shear pin may be broken when the tip meets an obstruction which may cause damage to the various elements of the machine.

I claim:

1. A hole digger comprising a pair of cylinders, a piston in each cylinder, a shaft connected to one piston and having an end projecting below its cylinder, a boring tool connected to the projecting end of the shaft, a cable for each piston having one end connected to its piston, a horizontal shaft extending over said cylinders, a pulley mounted above each piston and fixed to the horizontal shaft, the other end of each cable being trained in opposite directions on the adjacently disposed pulley and connected thereto, a housing enclosing the pulleys and provided with a fluid chamber for each cylinder and in communication therewith, means for supplying each chamber with fluid under pressure, a valve for controlling the flow of fluid to and from the chambers in alternation in such a manner that when one chamber is exhausting the other chamber is being supplied with fluid.

2. A hole digger comprising a housing having a pair of chambers therein, a cylinder for each chamber, each chamber being in communication with its respective cylinder, the top of the housing having inlet and outlet passages for a liquid under pressure to and from the chambers, a valve controlling the flow of liquidto one chamber in alternation with the outflow of liquid from the other chamber, a piston in one cylinder being movable towards one end of said cylinder while the other piston is being moved towards the opposite end of its cylinder, a pulley located over each cylinder, a shaft connecting the pulleys for simultaneous rotation, a cable trained over one pulley in one direction and connected to one piston, a cable trained over the other pulley in a reverse manner and connected to the other piston so that as one piston is elevated the other piston is lowered, means supplying liquid under pressure to the inlet passage, a shaft connected to one piston and reciprocated thereby in one direction, a boring tool on the shaft, and means for rotating said shaft.

3. A post hole digger comprising a vehicle chassis provided with a source of power, a supporting frame mounted on the chassis having vertically disposed bearings, a sleeve carried therein provided with a gear wheel and driving connections between it and the source of power, a drill stem movable longitudinally through the stem and rotated thereby, a cylinder carried by the frameand enclosing the upper end of said stem and provided with a piston head for moving the stem outwardly of the cylinder, a second cylinder having a piston therein, a head connecting the upper ends of the cylinders havin an enlarged chamber for each cylinder, a shaft extending through the chambers and a pulley in each chamber fixed to the shaft, cables attached to the pistons and trained over said pulleys to effect reciprocal movement of the pistons in opposite directions, said head also having pairs of pressure inlet and exhaust ports for each cylinder, a valve for controlling them and a drilling bit attached to the stem.

WALTER JAMES McGARR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,014,477 Humiston Jan. 9, 1912 2,179,316 Anderson Nov. 7, 1939 2,188,107 Caldwell et al Jan. 23, 1940 2,192,909 Hoffer Mar. 12, 1940 

